Increased vasoconstrictor sensitivity in obstructive sleep apnea.

We studied vasoconstrictor sensitivity and cholinergic responsiveness of the forearm vasculature in 10 male patients with obstructive sleep apnea (OSA) and 10 healthy controls. Subjects with regular medication, known arterial hypertension, diabetes mellitus, or dyslipidemia were not included in this study. Age, body mass index, blood pressure, blood glucose, serum lipids, and baseline forearm vascular conductance (derived from venous occlusion plethysmography and intra-arterial blood pressure measurement) did not differ significantly between these two groups. With use of three dosage steps each, angiotensin II and acetylcholine were successively infused into the brachial artery. During infusion of angiotensin II, mean conductance was 39.6% lower (P = 0.002) in the OSA patients compared with that in the control subjects. Vascular responsiveness to increasing dosages of acetylcholine was not significantly altered in the OSA group. These findings suggest an enhanced vasoconstrictor sensitivity in the forearm vasculature in OSA. The hypothesis that endothelial function in OSA is impaired independently of other cardiovascular risk factors is not supported by the present results.